Progress on materials and scaffold fabrications applied to esophageal tissue engineering

Resveratrol promotes the differentiation of human umbilical cord mesenchymal stem cells into esophageal fibroblasts via AKT signaling pathway

Objectives: Resveratrol has been implicated in the differentiation and development of human umbilical cord mesenchymal stem cells. The differentiation of into esophageal fibroblasts is a promising strategy for esophageal tissue engineering. However, the pharmacological effect and underlying mechanism of resveratrol on human umbilical cord mesenchymal stem cells differentiation are unknown. Here, we investigated the effects and mechanism of resveratrol on the differentiation of human umbilical cord mesenchymal stem cells. Methods: Using a transwell-membrane coculture system to culture human umbilical cord mesenchymal stem cells and esophageal fibroblasts, we examined how resveratrol act on the differentiation of human umbilical cord mesenchymal stem cells. Immunocytochemistry, Sirius red staining, quantitative real-time PCR, and Western blotting were performed to examine collagen synthesis and possible signaling pathways in human umbilical cord mesenchymal stem cells. Results: We found that resveratrol promoted collagen synthesis and AKT phosphorylation. However, co-treatment of cells with resveratrol and the PI3K inhibitor LY294002 inhibited collagen synthesis and AKT phosphorylation. We demonstrated that resveratrol down-regulated the expression of IL-6, TGF-β, caspase-9, and Bax by activating the AKT pathway in human umbilical cord mesenchymal stem cell. Furthermore, resveratrol inhibited phosphorylated NF-ĸB in human umbilical cord mesenchymal stem cells. Conclusion: Our data suggest that resveratrol promotes the differentiation of human umbilical cord mesenchymal stem cells into fibroblasts. The underlying mechanism is associated with the downregulation of IL-6 and TGF-β via the AKT pathway and by inhibiting the NF-ĸB pathway. Resveratrol may be useful for esophageal tissue engineering.

Reactive Cell Electrospinning of Anisotropically Aligned and Bilayer Hydrogel Nanofiber Networks

Structured hydrogels that incorporate aligned nanofibrous morphologies have been demonstrated to better replicate the structures of native extracellular matrices and thus their function in guiding cell responses. However, current techniques for nanofiber fabrication are limited in their ability to create hydrogel scaffolds with tunable directional alignments and cell types/densities, as required to reproduce more complex native tissue structures. Herein, we leverage a reactive cell electrospinning technique based on the dynamic covalent cross-linking of poly(ethylene glycol methacrylate (POEGMA) precursor polymers to fabricate aligned hydrogel nanofibers that can be directly loaded with cells during the electrospinning process. The scaffolds were found to support high C2C12 myoblast viabilities greater than 85% over 14 days, with changes in the electrospinning collector allowing for the single-step fabrication of nonaligned, aligned, or cross-aligned nanofibrous networks. Cell aspect ratios on aligned scaffolds were found on average to be 27% higher compared to those on nonaligned scaffolds; furthermore, cell-loaded bilayer scaffolds with perpendicular fiber alignments showed evidence of enabling localized directional cell responses to individual layer fiber directions while avoiding delamination between the layers. This fabrication approach thus offers potential for better mimicking the structure and thus function of aligned and multilayered tissues (e.g., smooth muscle, neural, or tendon tissues).

Biologic Mechanisms of Macrophage Phenotypes Responding to Infection and the Novel Therapies to Moderate Inflammation

Pro-inflammatory and anti-inflammatory types are the main phenotypes of the macrophage, which are commonly notified as M1 and M2, respectively. The alteration of macrophage phenotypes and the progression of inflammation are intimately associated; both phenotypes usually coexist throughout the whole inflammation stage, involving the transduction of intracellular signals and the secretion of extracellular cytokines. This paper aims to address the interaction of macrophages and surrounding cells and tissues with inflammation-related diseases and clarify the crosstalk of signal pathways relevant to the phenotypic metamorphosis of macrophages. On these bases, some novel therapeutic methods are proposed for regulating inflammation through monitoring the transition of macrophage phenotypes so as to prevent the negative effects of antibiotic drugs utilized in the long term in the clinic. This information will be quite beneficial for the diagnosis and treatment of inflammation-related diseases like pneumonia and other disorders involving macrophages.

Trends in 3D bioprinting for esophageal tissue repair and reconstruction

In esophageal pathologies, such as esophageal atresia, cancers, caustic burns, or post-operative stenosis, esophageal replacement is performed by using parts of the gastrointestinal tract to restore nutritional autonomy. However, this surgical procedure most often does not lead to complete functional recovery and is instead associated with many complications resulting in a decrease in the quality of life and survival rate. Esophageal tissue engineering (ETE) aims at repairing the defective esophagus and is considered as a promising therapeutic alternative. Noteworthy progress has recently been made in the ETE research area but strong challenges remain to replicate the structural and functional integrity of the esophagus with the approaches currently being developed. Within this context, 3D bioprinting is emerging as a new technology to facilitate the patterning of both cellular and acellular bioinks into well-organized 3D functional structures. Here, we present a comprehensive overview of the recent advances in tissue engineering for esophageal reconstruction with a specific focus on 3D bioprinting approaches in ETE. Current biofabrication techniques and bioink features are highlighted, and these are discussed in view of the complexity of the native esophagus that the designed substitute needs to replace. Finally, perspectives on recent strategies for fabricating other tubular organ substitutes via 3D bioprinting are discussed briefly for their potential in ETE applications.

Regeneration of the oesophageal muscle layer from oesophagus acellular matrix scaffold using adipose-derived stem cells

This study explored the feasibility of constructing a tissue engineered muscle layer in the oesophagus using oesophageal acellular matrix (OAM) scaffolds and human aortic smooth muscle cells (hASMCs) or human adipose-derived stem cells (hASCs). The second objective was to investigate the effect of hypoxic preconditioning of seeding cells on cell viability and migration depth. Our results demonstrated that hASMCs and hASCs could attach and adhere to the decellularized OAM scaffold and survive and proliferate for at least 7 days depending on the growth conditions. This indicates adipose-derived stem cells (ASCs) have the potential to substitute for smooth muscle cells (SMCs) in the construction of tissue engineered oesophageal muscle layers.

Development of an omentum-cultured oesophageal scaffold reinforced by a 3D-printed ring: feasibility of an in vivo bioreactor

Current treatments of oesophageal diseases, such as carcinoma, congenital abnormality or trauma, require surgical intervention and oesophageal reconstruction with the stomach, jejunum or colon. However, serious side effects are possible with each treatment option. Despite tissue engineering promising to be an effective regenerative strategy, no functional solution currently exists for oesophageal reconstruction. Here, we developed an omentum-cultured oesophageal scaffold reinforced by a 3D-printed ring. The nano-structured scaffolds were wrapped into the omentum of rats and orthotopically transplanted for the repair of circumferential oesophageal defects two weeks later. The artificial oesophagus exhibited complete healing of the surgically created circumferential defects by the second week. The integration of the omentum-cultured oesophageal scaffold and the regenerative tissue remained intact. Macroscopically, there was no evidence of a fistula, perforation, abscess formation or surrounding soft-tissue necrosis. The omentum-cultured nano-structure scaffold reinforced by a 3D-printed ring is a more practical model with better vascularization for artificial neo-oesophagus reconstruction in a rat model.

Esophageal reconstruction: Combined application of muscle tissue flap and inner chitosan tube stent in rabbits

BACKGROUND

Esophageal reconstruction is the key issue in esophageal surgery. However, currently there is no satisfied technique to repair esophagus after surgery.

OBJECTIVE

To combine an inner chitosan stent and a muscle tissue with vascular pedicle to repair the esophageal defect in cervical segment.

METHODS

Esophageal defect was repaired using the combination of a muscle tissue flap and a chitosan tube stent in experimental group while only muscle tissue flap was utilized in controls for comparison. One animal in each group was sacrificed at week 3, 6 and 9 after operation respectively to exam the healing status. Barium X-ray was used to evaluate the esophageal status in 12 weeks.

RESULTS

Histology showed the inflammatory response in 3 weeks after surgery, the chitosan stent was partially absorbed in 6 weeks, and there was no obvious fibrotic proliferation in experimental group; while the fibrotic proliferation and esophageal stenosis were obvious in controls, the chitosan stent was completely absorbed in 9 weeks, and squamous epidermis cells were observed. Twelve weeks later, the barium swallow went smoothly through the esophagus with noticeable peristalsis in the experimental group; esophageal stenosis without peristalsis was observed in controls.

CONCLUSION

The combination of chitosan stent and muscle tissue flap is feasible to reconstruct a partial defect in esophagus.

Constitution and in vivo test of micro-porous tubular scaffold for esophageal tissue engineering

Current clinical techniques in treating long-gap esophageal defects often lead to complications and high morbidity. Aiming at long-gap synthetic esophageal substitute, we had synthesized a biodegradable copolymer, poly(L-lactide-co-caprolactone) (PLLC), with low glass transition temperature. In this work, we developed a tubular PLLC porous scaffold using a self-designed tubular mold and thermal induced phase separation (TIPS) method. In order to enhance the interaction between tissue and scaffold, fibrin, a natural fibrous protein derived from blood fibrinogen, was coated on the scaffold circumferential surface. The fibrin density was measured to be 1.23 ± 0.04 mg/cm2. Primary epithelial cell culture demonstrated the improved in vitro biocompatibility. In animal study with partial scaffold implantation, in situ mucosa regeneration was observed along the degradation of the scaffold. These indicate that fibrin incorporated PLLC scaffold can greatly improve epithelial regeneration in esophagus repair, therefore serve as a good candidate for long-term evaluation of post-implantation at excision site.

Difficult esophageal atresia: trick and treat

Although most patients with esophageal atresia (EA) and tracheo-esophageal fistula (TEF) may benefit from "standard" management, which is deferred emergency surgery, some may present unexpected elements that change this paradigm. Birth weight, associated anomalies, and long gap can influence the therapeutic schedule of the patients with EA/TEF and can make their treatment tricky. As a consequence, detailed information on these aspects gives the power to develop a decision-making process as correct as possible. In this article, we will review the most important factors influencing the treatment of patients with EA/TEF and will share our experience on the diagnostic and therapeutic tips that may provide pivotal help in the management of such patients.

Photocrosslinked ultrathin anionic polysaccharide supports for accelerated growth of human mesenchymal stem cells

OBJECTIVES

Properties of cell culture supports obtained from ultrathin multilayer films containing anionic natural polysaccharides (PSacs) and a synthetic polycation were studied.

MATERIALS AND METHODS

Supports were prepared via a layer-by-layer (LbL) self-assembly deposition method. Polymers used were: heparin (Hep), chondroitin sulphate (CS), hyaluronic acid (HA), and ι-carrageenan (Car) as polyanions, and diazoresin (DR) as a polycation. PSac layers were crosslinked with DR layers by irradiation with UV light absorbed by DR resin.

RESULTS

DR/PSac films are very efficient cell culture growth supports as found from experiments with human mesenchymal stem cells (hMSCs). Irradiation of the films resulted in changing zeta potential of outermost layers of both DR and PSac to more negative values, and in increased film hydrophobicity, as found from the contact angle measurements. Photocrosslinking of the supports led to their increased stability.

CONCLUSIONS

The supports allow for obtaining intact cell monolayers faster than when typical polystyrene tissue culture plates are used. Moreover, these monolayers spontaneously detach permitting formation of new cell layers on these surfaces relatively early during culture, compared to cells cultured on commonly used tissue culture plastic.

Grafting of bovine serum albumin proteins on plasma-modified polymers for potential application in tissue engineering

In this work, an influence of bovine serum albumin proteins grafting on the surface properties of plasma-treated polyethylene and poly-l-lactic acid was studied. The interaction of the vascular smooth muscle cells with the modified polymer surface was determined. The surface properties were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, nano-LC-ESI-Q-TOF mass spectrometry, electrokinetic analysis, and goniometry. One of the motivations for this work is the idea that by the interaction of the cell with substrate surface, the proteins will form an interlayer between the cell and the substrate. It was proven that when interacting with the plasma-treated high-density polyethylene and poly-l-lactic acid, the bovine serum albumin protein is grafted on the polymer surface. Since the proteins are bonded to the substrate surface, they can stimulate cell adhesion and proliferation.

Seamless vascularized large-diameter tubular collagen scaffolds reinforced with polymer knittings for esophageal regenerative medicine

A clinical demand exists for alternatives to repair the esophagus in case of congenital defects, cancer, or trauma. A seamless biocompatible off-the-shelf large-diameter tubular scaffold, which is accessible for vascularization, could set the stage for regenerative medicine of the esophagus. The use of seamless scaffolds eliminates the error-prone tubularization step, which is necessary when emanating from flat scaffolds. In this study, we developed and characterized three different types of seamless tubular scaffolds, and evaluated in vivo tissue compatibility, including vascularization by omental wrapping. Scaffolds (luminal Ø ∼ 1.5 cm) were constructed using freezing, lyophilizing, and cross-linking techniques and included (1) single-layered porous collagen scaffold, (2) dual-layered (porous+dense) collagen scaffold, and (3) hybrid scaffold (collagen+incorporated polycaprolacton knitting). The latter had an ultimate tensile strength comparable to a porcine esophagus. To induce rapid vascularization, scaffolds were implanted in the omentum of sheep using a wrapping technique. After 6 weeks of biocompatibility, vascularization, calcification, and hypoxia were evaluated using immunohistochemistry. Scaffolds were biocompatible, and cellular influx and ingrowth of blood vessels were observed throughout the whole scaffold. No calcification was observed, and slight hypoxic conditions were detected only in the direct vicinity of the polymer knitting. It is concluded that seamless large-diameter tubular collagen-based scaffolds can be constructed and vascularized in vivo. Such scaffolds provide novel tools for esophageal reconstruction.

Synthesis, characterization and cytocompatibility of a degradable polymer using ferric catalyst for esophageal tissue engineering

This study focused on the synthesis, characterization and cytocompatibility of a biodegradable polymer by the cross-linking from poly(ethylene glycol-co-lactide) dimethacrylate (PLEGDMA), polyethylene glycol diacrylate (PEGDA) and N-isopropylacrylamide, where PLEGDMA was synthesized by ring-opening oligomerization of poly(ethylene glycol) with different molecular weights (Mn = 400, 600, 1000, 2000 Da) and L-lactide using low toxic iron(III) acetylacetonate (Fe(acac)3) as the catalyst and subsequently being terminated with dimethacrylate. The product, PLEGDMA, was analyzed to confirm its chemistry using FTIR spectroscopy, (1)H NMR spectra and gel permeation chromatography etc. The thermodynamic properties, mechanical behaviors, surface hydrophilicity, degradability and cytotoxicity of the cross-linked product were evaluated by differential scanning calorimetry, tensile tests, contact angle measurements and cell cultures. The effects of reaction variables such as PEGDA content and reactants ratio were optimized to achieve a material with low glass transition temperature (Tg), high wettability and preferable mechanical characteristics. Using a tubular mould which has been patented in our group, a tubular scaffold with predetermined dimension and pattern was fabricated, which aims at guiding the growth and phenotype regulation of esophageal primary cells like fibroblast and smooth muscle cell towards fabricating tissue engineered esophagus in future.